Drug maker Dendreon (DNDN) was hot stuff over the last two years. The shares skyrocketed amid widespread excitement over Provenge, a cutting-edge prostate cancer treatment approved by the FDA in April that sell-side analysts widely expected to eventually generate blockbuster sales. But today, Dendreonâs stock price plunged more than 64% to just under $13 a share after the company disclosed that Provenge sales are growing slower than expected and yanked its 2011 revenue estimate, prompting Wall Street to reassess its view of the biotech company.